Sams Teach Yourself Java in 21 Days, Sixth Edition

Day 3. Working with Objects

Java is primarily an object-oriented programming language. When you do work in Java, you use objects to get the job done. You create objects, modify them, change their variables, call their methods, and combine them with other objects. You develop classes, create objects out of those classes, and use them with other classes and objects.

Today, you work extensively with objects as the following topics are covered:

• Creating objects

• Testing and modifying their class and instance variables

• Calling an object’s methods

• Converting objects from one class to another

Creating New Objects

When you write a Java program, you define a set of classes. As you learned during Day 1, “Getting Started with Java,” classes are templates ...